Various types of multi-function end effectors having a tool changing ability are known. One type of multi-function end effector has a number of tool modules each having a tool holding device coupled with a drive motor. The modules can be interchanged on a feeding block, which in turn can advance and retract a tool module for performing work operations. A drawback of this type of end effector is that a plurality of drive motors are required. In order to keep the overall size and weight of the end effector reasonably low, the drive motors must be relatively small and hence are limited in power. This type of end effector thus is best suited to fairly light work operations that do not require large machining forces.
Another known type of multi-function end effector employs an indexing tool magazine holding a plurality of tool holders that can be interchanged in a spindle of the end effector. The spindle is driven by a single drive, thus eliminating the need for a plurality of drive motors. Examples of such end effectors can be found in U.S. Pat. No. 5,372,568 to Matsuoka, U.S. Pat. No. 4,995,148 to Bonomi et al., U.S. Pat. No. 4,835,838 to Hirose, and U.S. Pat. No. 4,309,809 to Yokoe et al. The Matsuoka, Hirose, and Yokoe end effectors employ a rotary indexing tool magazine that is mounted to one side of the spindle. The magazine has a plurality of grippers each operable to releasably grip a tool holder. In the Hirose and Yokoe patents, the magazine is rotated to place a selected one of the grippers in a position in which an actuator can engage the gripper and pivotably move the gripper so as to move the tool holder into a position allowing the spindle to be moved to engage and clamp onto the tool holder. The actuator then pivots the gripper back to its starting position. The Matsuoka end effector indexes the selected gripper to a position nearest the spindle with the tool holder axis parallel to and spaced above the axis of the spindle, and then the spindle is translated upward by a drive mechanism toward the tool holder until the spindle is coaxially aligned with the tool holder. The entire tool magazine is then translated horizontally by another drive mechanism so as to insert the tool holder into the spindle. A cam arrangement connected with a draw bar of a clamping mechanism of the spindle causes the draw bar to translate upon subsequent downward translation of the spindle such that the draw bar clamps the tool holder in the spindle.
The Bonomi end effector employs a linearly movable tool magazine or shuttle that holds a plurality of tools. The shuttle is translated to index a selected one of the tools into coaxial alignment with the tool head of the end effector. The shuttle includes four stations. One station comprises a hole through which a drill mounted in the spindle of the end effector can pass for drilling a hole in a workpiece. In the other three stations are a sealant applicator for applying sealant to the hole in the workpiece, a rivet feed mechanism for feeding a rivet into a position enabling it to be inserted into the hole in the workpiece by directing a blast of compressed air through the tool head against the rivet, and a bucking bar bushing for upsetting the rivet in the hole. The drill remains mounted in the spindle throughout all of these operations, and is retracted when the sealant applicator, rivet feed mechanism, and bucking bar bushing are in use. This end effector requires access to both sides of the workpiece into which rivets are to be installed. In some applications, it may be difficult or impossible to access both sides of a workpiece.
There is a need in the art for a multi-function end effector that can install rivets or similar types of fasteners and that requires access to only one side of the workpiece.